#include <stdio.h>

int mystrlen(char *);
void revstring(char *, int *);
int main(void)
{
    char strinp[40];
    int charcount;

    printf("Enter a string: ");
    scanf("%[^\n]s", strinp);

    charcount = mystrlen(strinp);

    revstring(strinp, &charcount);
}

int mystrlen(char strinp [])
{
    int count = 0;
    char *ptr;
    ptr = strinp;
    while (strinp[count] != '\0') {
        count++;
    }
    return count;
}

void revstring(char strinp[], int *charcount)
{
    char *ptr;
    ptr = strinp;
    while (*charcount != -1) {
        printf("%c", *(ptr + *charcount));
        *charcount--;
    }
}